答复: some questions about gfapi glfs_open

[Gong XiaoHui <xhgong@xxxxxxxxxxx>]

I want to test multi-client read/write the remote file on GlusterFS,
My test code:

bool testGFAPI(){
	std::string volName = "rvonly";
	std::string serverIP = "10.100.3.110";
	int port = 24007;
	glfs_t* glfs = glfs_new (volName.c_str());
	if (glfs == NULL) {
		std::cout<<"glfs_new("<<volName<<") return NULL"<<std::endl;
		return false;
	}
	int ret = glfs_set_volfile_server (glfs, "tcp", serverIP.c_str(), port);
	if (ret){
		std::cout<<"glfs_set_volfile_server return NULL"<<std::endl;
		return false;
	}

	ret = glfs_set_logging (glfs, "/dev/stderr", 1);

	ret = glfs_init (glfs);
	if (ret){
		std::cout<<"glfs_init return "<<ret<<std::endl;
		return false;
	}

	glfs_setfsuid (0);
	glfs_setfsgid (0);

	const char* path = "test.txt";
	glfs_fd_t * writefd = glfs_open (glfs, path, O_WRONLY|O_TRUNC);
	if (writefd){
		glfs_write(writefd, (void*)"abcd", 4, 0);
   }else{
	   std::cout<<"open write test.txt error"<<std::endl;
    }

	char data[1024] = {0};
	glfs_fd_t * readfd = glfs_open (glfs, path, O_RDONLY);			// I need this return NULL, but it return an available fd,
	if (readfd){
		glfs_read(readfd,data, 4, 0);			//data[] =" abcd"
   }else{
	   std::cout<<"open read test.txt error"<<std::endl;
	}

	if (writefd) glfs_close (writefd);
	if (readfd) glfs_close (readfd);

	if (glfs) glfs_fini (glfs);
	return true;
}

That is all, thank you.

-----邮件原件-----
发件人: Vijay Bellur [mailto:vbellur@xxxxxxxxxx] 
发送时间: 2014年6月16日 19:03
收件人: Gong XiaoHui; Niels de Vos
抄送: Gluster Devel
主题: Re: some questions about gfapi glfs_open

On 06/16/2014 08:47 AM, Gong XiaoHui wrote:
> Hi
> 
>    When I use the libgfapi, I need to open and write a file, called ” 
> glfs_open(glfs, path, O_WRONLY|O_TRUNC);” return a glfs_fd_t,
> 
> before I close it ,there is a new request to read the same file,
> 
> I think the read request return NULL,

Does glfs_read() return -1? If so, this seems to be in line with expected behavior. Is there any reason for your application to send read on a fd that has been opened with O_WRONLY?


> but if I call “glfs_open(glfs,
> path, O_RDONLY);”,it return a available glfs_fd_t, so what should I do 
> to resolve this problem?
> 

Opening fd with O_RDWR | O_TRUNC seems to be the right thing to do if
both read and write operations are expected on the fd.

-Vijay

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